Lesson 1 rock weathering
★三段：①Water may fill a crack in a rock ;it freezes when it is very cold and,in doing so,makes the crack wider。
②Gradually little pieces of rock break away。
We should expect rocks to be broken in this way near the tops of high mountains,where it is very cold。
③The little pieces of rock which are broken off from hills and mountains roll down into the valleys,and we sometimes find great heaps of rough,sharp stones near the bottom of mountain。
①水可以充满岩石裂缝，严寒时水会结冰，这种现象使裂缝加大②岩石碎片逐渐剥落下来，我们可以想象严寒的山顶附近的岩石就是这样破裂的。
③从大小山顶上破碎的岩石碎块滚落到山谷，因而有时我们会在山脚附近发现大堆粗糙锋利的石块。
★四段：①The wind causes much wearing of rocks,particularly if sand and dust are blown along by it。
②If the wind blows over sandy country,such as deserts and beaches,it picks up quite a lot of sand and carries it along。
③The particles of sand rub,scratch and cut the rocks against which they are blown。
Soft rocks may be gradually worn away and harder rocks are rubbed so that they become smooth and shiny。
④Sometimes a rock is made into a very strange shape because softer parts are worn away and harder parts are left。
⑤The wind near the ground carries most sand with it and so wears the lower parts of big masses of rock most。
The lower part of a cliff may be worn away and then,in time,the upper part falls down。
①风使岩石遭到磨蚀，风里裹着沙土和尘土吹来时尤其如此②如果风从沙漠和海滩等多沙地带吹过会卷走大量沙土。
③这些沙粒吹到岩石上会刮削这些岩石。
硬度低的岩石被磨损掉了。
坚硬的则磨得锃光溜滑。
④有时一块岩石被磨成奇形怪状，因为软的部分被磨损硬的部分被留下来。
⑤靠近地面的风带起的沙最多，因此下部岩石磨蚀得最厉害。
一个悬崖底部会被磨蚀掉，总有一天，崖顶会倒塌下来。
★五段：①Must wearing and breaking of rocks takes place on the seashore; for the action of the sea is very powerful。
②As you stand on a beach,you can hear and see the sea at its work。
③stone are dragged up and down beach, and worn so that they become round and cliffs。
④The mere force of the water would slowly wear the cliffs,but this damage is small compared with that caused by the stones and sand which the water throws against them。
①海边发生大量岩石磨蚀和破坏的情况，因为海的作用是很大的，②当你站在海滩上时就可以听到和看到大海在起作用③石块在海滩上被推上推下磨得又圆又光。
在海岸的某些地方，海浪抽打着石崖。
④仅仅是海水的微小力量也会慢慢磨损石崖。
但这种损坏与海水裹着沙石冲击石崖造成的损失相比就微不足道了。
Lesson 2 soil development
★二段：①From the broadest point of view, pedology is a study of the development of soil material。
②Soil material may be defined as the material occupying the outermost part of the earth’s crust and possessing distinct mineralogical and chemical properties resulting from certain inheritance factors,from its unique position on the surface of the earth,and from the environmental factors existing at that position。
㈠就广义而言，土壤学是一门研究土壤物质发展的学科。
②土壤物质可以说是存在地球最外层的物质，它具有明显的矿物学和化学特性。
这些特性是因为一定的遗传因素，地球表面的特定位置和在这些位置作用的环境因素的影响而产生的。
①thus one can study the development of a given soil property of a soil material from a fixed position with respect to the surface as it varies from locality ,②such as nitrogen content of the surface 6 inches as it is affected by a variation in temperature,or one can study the variation of the soil material as it is affected by its position with respect to the surface at any one site。
③Recognition of the variation of soil material with depth as a result of developmental processes is one of the unique contributions of pedology。
①因此我们可以从一定深度出发,研究土壤某一特定性质的发展因地区而不同的现象。
②例如我们研究6英尺范围N的含量受温度影响，我们也可以研究地面下不同深度任意位置的土壤变异情况。
③认识土壤由于形成过程所形成的不同深度的变异乃是土壤学主要的贡献之一。
★三段：Many pedologists believe that a soil should be defined by the unique variation in its properties with depth and that all soil materials extending from the surface downward to a point where the properties remain uniform be considered as one body, termed the soil profile; the individual layers of soil material that exhibit distinct variations with depth are termed soil horizons。
许多土壤学家认为土壤可以按照因深度不同而发生性质上的独特变化而定义。
并把从土壤表面向下到达特征均一的的地方看作一个整体，并被称为土壤剖面，因深度不同而有显著差别的土壤物质个别层次成为土层。
Soil is an independent, dynamic body of nature that…….act upon it土壤是一种独立的运动的自然体，根据作用于它的力不同获得各种性质。
Recognition of this fact established……pedology希尔加德和道库恰耶夫认识到这个事实，他们被尊称为土壤学的奠基者
These men were the first to recognize……time of reaction他们最先认识到许多土壤性质是某些物理化学作用的产物，而这些物理化学性质不仅受岩石和岩石物质的影响同时也受气候、地形、植被、作用时间的影响
Through their efforts and efforts of ……earth saiences通过他们以及追随他们的科学家的努力土壤学已成为地学的重要分支
Lesson 3 air pollution
★五段：①Control of air pollution injury to vegetation is a difficult task。
Sources may be far from the areas where injury occurs and commonly cross town, county, state, and sometimes national boundaries。
②Various federal, state, and local government regulatory agencies are involves in monitoring pollution levels in an attempt to reduce emissions。
③Strict enforcement of air pollution control laws, however, is difficult。
Planting of species resistant to phytotoxic air pollutants, therefore, is the most widely used measure to minimize injury where pollutants are known to occur。
④Application of balanced fertilizers to increase vigor has been recently shown to decrease injury on plants after exposure to some common pollutant。
①防止空气污染对植物的损害是一项艰难的工作。
污染源可能是距受害地区很远，可能穿过镇，县，州甚至是国界。
②为了减少排放物，各联邦，州，地方政府的立法机构也被牵涉到监控污染的行列。
③然而严格实施空气污染防治法规是困难的，所以在已知有污染地区栽植对毒害植物的空气污染物抗性大的树种是减轻危害最广泛应用的措施。
④近来平衡施肥增强植物活力，被证明可以减少暴露于通常污染物中的植物的损害。
Air pollutants may be classified…….diffuse oxidant根据来源空气污染可以分为两类点源污染排放物、扩散氧
化剂
Point source emissions come from ……burning areas点源排放物来自同一个地方大烟囱或燃烧区
Diffuse oxidants are formed…..by sunlight扩散氧化剂在广阔大气中通过阳光作用由各种氧化反应形成
These diffuse pollutants are also…..oxidants这些扩散氧化剂也被称为化学氧化剂
Lesson 4 —Plant Nutrition
★一段: ①A rational system of agriculture cannot be formed without the application of scientific principles ; for such a system must be based on an exact acquaintance with the means of nutrition of vegetables, and with the influence of soils and action of manure upon them 。
”②Such were the thoughts expressed by Justus Von Liebig more than 100 years ago and which led him to examine the then existing theories of plant nutrition ,embark on theories of his own , and stress the significance of plant analysis as a means of measuring the needs of plants。
①不应用科学原理就不能形成一个合理的农业体系，因为这个体系必须对下列知识有正确了解为基础，即熟悉植物营养的途径，了解土壤对植物的影响和肥料对植物的影的作用。
②这是贾斯托斯?冯?李比希100多年前的理想，这个理论引导他去研究当时存在的植物营养学说，并从事他自己的学说，且使他重视植物分析作为测定植物需要的方法的意义。
★二段：①As late as the 19th century the natural philosophers believed that the nutrients required for plant growth existed in the soil in a state needing no specific plant metabolism。
②This theory came to be known as the “humus theory”。
③It was supported by the observation of the favorable effect of animal manures and plant residues on plant growth and stipulated that plants feed upon substances which are similar to them in nature。
④The roots were supposed to extract the “humus” from the soil and transform it into plant substance through combination with water。
⑤This process was considered analogous to animal nutrition in that both plants and animals were feeding on complex organic bodies。
⑥ Minerals in plants were considered nonessential but were believed to act as stimulants rather than nutrients 。
⑦They were considered as mere accidental plant constituents or skeleton substances, similar to the bones of animals。
①迟至19世纪，自然哲学家们还认为植物生长所需的养料以不需要进行特殊植物代谢作用的形态存在于土壤中。
②这个学说成为腐殖质学说。
③这是因为观察动物厩肥和植物残渣对植物生长的有利作用而被支持，并推断营养植物的物质和这些物质在本质上是相似的。
④他们推测根从土壤中吸取腐殖质后经与水结合就把他们转换成植物物质。
⑤他们认为这一过程和动物营养相似，也就是动物和植物之间都是以复合有机体来营养的。
⑥矿物质在植物中被认为是非必须的，而且认为他们的作用不是在于营养，而是刺激。
⑦这些矿物质被认为仅仅是偶然的植物组成或类似于动物骨骼的骨骼物质。
★三段：①Carbon was then considered to be derived solely from humus。
But rapidly accumulating information began to point to the true importance of the role of leaves and roots in plant nutrition。
②D E Saussure in 1804established beyond doubt that green plants assimilate carbon from the carbon dioxide of the atmosphere。
③He likewise believed that the soil furnished a small but essential part of the plant
nutrients, including nitrogen and the mineral constituents。
④Sprengel likewise concluded that plants obtain their minerals directly from the soil and there is no basis for such a concept as the humus heory。
⑤But the humus theory did not find an end until 1840, when Liebig pointed out that , since humus arised from decay of plants ,plants must have preceded the mumus。
①那时碳素被完全认为是从腐殖质中来的。
但积累起来的知识很快指出，叶和根在植物营养中的重要作用。
②1840年德索尔无可质疑地肯定了绿色植物可以从大气中的CO2中同化碳。
③他同样认为土壤提供植物养料的量虽少，但都是必须的物质，其中包括N2和矿物质成分。
④施普伦格尔也得出了植物直接从土壤中得到腐殖质的结论，并认为腐殖质概念是没有基础的。
⑤但是腐殖质学说却一直到1840年才告终了，当时李比希指出由于腐殖质是植物腐烂后产生的，故必然是现有植物后有腐殖质。
★四段：①The real significance of organic matter in plant nutrition was brought out later by the work of soil microbiologists who showed that the decay of organic matter releases nitrogen and mineral nutrients in forms available for plants 。
②Decomposition products of organic matter have also been shown to have a beneficial effect on soil aggregation , and organic matter itself has been shown to increase the water-holding capacity , cation exchange capacity, and availability of nutrients, notably phosphorus and pstassium。
③Decomposition of organic matter liberates carbon dioxide, which, when diffused in the aboveground atmosphere, serves as a source of carbon for the growing plant。
①有机质在植物营养中的真正含义是由稍晚的土壤微生物学家提出的，他们指出植物有机物质腐烂释放出植物可以利用形态的N和矿质养料。
②有机质的分解产物被指出对土壤团聚作用有良好的影响，且有机质本身又被证明可增加持水量，阳离子交换量和养分特别是p和k 的有效性。
③有机质分解释放出CO2，当它扩散进入到地面以上的大气层中时，就可以作为植物生长所必须的C的来源。
★五段：①Before Liebig’s activities and ever since, soil scientists have sought to find the key to a correlation between chemical properties of soil and the growth and nutrient content of plants 。
②For many years these correlations were sought in the total analysis of soils, fractional analysis including both strong and week acid extractions, analysis of the soil solution ,and analysis of the exchangeable cations and anions and anions。
③Great stress was also placed on the analysis of the plant as a means of determining the effect of soil upon nutrition and growth。
④To get at the problem some investigators used the entire plants for analysis , others used parts such as leaves or water-solubleconstituents。
①在李比希活动的前后时期，土壤科学家们曾试图找出土壤化学性质与植物生长及植物养料含量之间的关键关系。
②许多年来，他们一直从土壤的全量分析，分级分析（强酸和弱酸浸提，土壤溶液分析，可交换阳离子和阴离子的分析等方面）寻找这些相互关系。
③用来检定土壤对植物营养和生长影响的植物分析方法，给予了很大重视。
④在这个问题上有些研究者用整个植物进行分析，另一些研究者应用植物的一部分例如叶子和柄，还有一些人只用弱酸溶性或水溶性的来分析。
★六段：①Many of the data thus obtained resulted in controversial and contradictory explanations。
②Many of the interrelationships involving nutrients in the soils and nutrients in the plant are still subjects of controversy。
③But because of increased precision of analytical tools, better control of environmental and nutritional
conditions for growing plants and a more comprehensive characterization of the soil-root ionic environment , these in teractions are beginning to be more clearly comprehended 。
④Use of radioactive isotopes, chelating agents, excised root techniques, the energy relationship concept of the ionic soil and plant colloid systems aids greatly in clarifying some of these interactions。
①由此得到的许多数据生产了许多相互争论和相互矛盾的解释。
②许多关于土壤中的养料和植物中的养料的相互关系依旧还是争论的课题。
③但由于分析工具日益精确，植物生长的环境和营养条件得到较好的控制以及对土壤根离子现状的特征有更多的了解，这种相关关系开始逐渐被了解。
④由于使用了放射性性同位素，鳌合剂，切根割技术和土壤和植物离子胶体系统的能量关系，就大大地帮助了人们对某些相互关系的澄清。
Lesson 5 fertilizers
★四段：①Great emphasis has recently been placed on the critical need for much more use of chemical fertilizers in the newly developing countries。
②Admittedly the need is great,but fertilizers are economically effective only if the correct kinds and amounts are used for each local kind of soil, and if the other practices needed to satisfy the other requirements for good harvests are adopted at the same time 。
③Similarly, full benefits cannot be expected from irrigation, or from terracing or bunding for run-off control,without good engineering designs and without fertilizers, good varieties, and pest control。
④Failure to grasp this vital principle of interactions is the greatest present technical handicap to agriculture development in the newly developing countries。
①近来非常强调在新近发展中国家迫切需使用更多的化肥。
②公认这种需要是大的，但只有据当地每种土壤种类，在品种和数量上合理使用化肥并同时采用保证丰收所需的其它措施，化肥才能发挥经济效益。
③同样的，如果没良好的工程设计和化肥，优良品种和害虫防治，也不能期望从灌溉控制冲刷的堤田，堤岸得到足够好处。
④不能掌握这种相互作用的重要原理乃是新近发展中国家目前农业发展上遇到的最大的技术障碍。
★八段：①The investigation of soil fertility and fertilizer use falls naturally into two sections :(a) long-term or basic investigation; and (b) short-term or ad hoc investigation;although the two overlap。
②A developing country, with rapidly growing problems of population and food supplies, cannot wait to solve long-term questions before beginning fertilizer use in practice。
③Such a country will have to do what many others have done before it :begin by taking what is known from investigations in other, comparable countries, and by pressing on with short-term research and demonstration。
④At the same time, such basic research can be instituted as is needed to keep fertilizer use on the right lines, and to be ready to deal with difficult problems as and when they arise。
①土肥和化肥使用研究自然划分为两个部分：（a）长期研究或基础研究；（b）短期研究。
虽然这两部分是互不重叠的。
②一个发展中国家，随人口和粮食供应的迅速增长，不可能等到长期研究问题解决后才在实际中使用化肥。
③这样一个国家将不得不做许多其它国家早已作过的事情，借鉴它国的资料，并加强本国预期研究和示范。
④同时，这样的基础研究为保证正确使用化肥并准备解决随时发生的问题，也要着手进行上述基础研究工作。
★九段：①Few people realize how widely crops differ in their fertilizer needs , how greatly soils can vary in available nutrient deficeencies and fertilizer requirements, and how large an influence climate and moisture-supply have on the effectiveness of
fertilizers。
②Consequently, although a great deal can be learned from the experience of other, similar countries , every country must have its own comprehensive fertilizer investigational programme。
③This relates particularly to the ad hoc problemsof the fertilizer needs of local crops and soils—which may even vary from one field to another, and which will certainly change with different soil areas。
①很少有人认识到各种作物对化肥需求的差别多么大。
各种土壤在有效养料缺乏方面和化肥需要量方面存在多大变化及气候和水分供应对化肥使用效果又有多大影响。
②因此，虽然从其它相似国家经验中可学到很多东西，但是每个国家仍必须有自己的综合性的化肥研究方案。
③这一点与当地作物和土壤对化肥需要的专题问题有特别密切关系。
这种需要甚至在各田块互不相同，这种研究随土壤，田地的不同而改变。
unfortunately, only a small fraction…..planting the need令人遗憾的是世上只有一小部分土壤能对清理土地翻耕土壤播种作出良好反应
The more highly developed and productive…..their crops农业制度发展越高生产力越强，对土壤的处理就越精细复杂；为增加生产农民必须改良土壤环境是其适应所种作物
The basic data on which ….soil chemists农民们工作所依据的基本资料将由土壤调查土壤化学家的工作提供
But their work, and that of the agricultural….and ensure their stability但是他们的工作及农业实验站的工作只是表明几乎所有的土壤都需径机械的化学的生物的处理来改良它们的产量和稳定性
There are at least four basic…..in the world世界上每公顷丰产田至少与以下四方面传统与规划条件有关
These are (a)a balanced…. 高产田植物营养元素的平衡供应(b)adequate moisture….植物土壤根系所需的足够的湿度和空气(c)kinds and varieties….能够对有利的土壤作出反应，并且有遗传潜力的作物种类和品种(d)adequate protection of soil….. and high winds 对土壤植物和那些以种植作物为饲料的牲畜保护，使其免受虫害及其他灾害，此外，还时常需采取特殊措施来保护有潜力的土壤，以免山洪暴雨海水和大风的侵蚀
Cultivators usually employ a combination …and climate etc耕作者通常采用多项措施相结合的方法，而任何一项措施的收效取决于其他的各项措施，而且取决于当地的气候和土壤等
No practice in soil management is …..harmful for anther在土壤管理中没有一项措施是普遍有利的，对一种土壤有利的措施可能对另外一种土壤是无效的或是绝对有害的
Lesson 6 Irrigation And water Use
★二段: ①Irrigation has been extensively practiced by the earliest known civilizations , but until recent years it had been regarded more as an art than a science。
②It was probably for lake of understanding of mang of the basic scientific principles of water use that many early civilizations dependent on irrigation eventually passed away。
③But although it is now possible to transform irrigation from an are into a science, so long as the control of his own water supply rests with the individual farmer , managing this resource will remain an art to some extent 。
④Moreover, in planning an designing irrigation schemes , attention to detail at every stage is perhaps more necessary than in any other modern agricultural practice。
⑤The development of water supplies may involve construction o imprsive an ultra-modern gineering strtres, but the developed water is often conveyed through
inefficient distribution systems to farmers who continue to irrigate in accordance with age-old practices and traditions little influenced by modern science and technology。
⑥Actually, new or improved irrigation projects should not be considered as complete until scientifically sound and well-engineered provisions have been made to apply water efficiently to the last crop row on the last farm and adequate arrangements made to remove any surplus water wherever necessary。
⑦ Intelligent application of today’s knowledge of irrigation science and technology would accelerate the effective utilization of water and soil resources insure an abundant and permanently successful irrigation agriculture, and reclaim many previously productive lands now waterlogged and often salinized。
①我们知道的最早的古老文明社会，灌溉被广泛的实施,但直到近些年,灌溉大多被看作一种技艺，而不是科学。
②大概因为对利用水的基本科学原理缺乏理解，许多依赖于水分灌溉的早期文明社会最终消失了。
③虽然把灌溉从一种技艺改为一种科学已经成为可能，但只要水供应的控制取决于个体农民，这一资源管理在某程度上仍是一种技艺。
④此外，在计划和设计灌溉方案上，注意每个时期的细节比注意其他现代化的农业措施显得更有必要。
水供应的发展可能包括建设令人惊叹的非现代化的工程结构，但是发展了的水通过效率很低的灌溉系统供给农民，而农民却是按很少受到科学技术影响的古老措施与传统习惯继续灌溉。
⑥实际上除非在科学上和工程建筑上所做的很好的准备，以便把水有效的供应到最后一个农场的最后一排作物上。
当还没再作出适应安排以使还没在需要的地方排出多余水之前，这种改良方案不应被认为是完美的。
⑦今天，有关灌溉科学技术最新应用将在加速水土资源的有效利用，这样会从有效的水分中供应中获得最高产量，会确保一种丰富的永远成功的灌溉农业，会开垦许多原本富饶现在渍水且常常盐化的土地。
★三段：①In general , irrigation is thought of as an end result of large and costly development works, often based on a multi-purpose scheme for optimizing the resources of a whole river basin, as in the Nile valley, or for bringing water to vast semi-arid regions such as the Golodnaya Steppe and other parts of Central Asia。
②But it need not always mean very large-scale constructional work, as was shown by an Italian paper on the effects of building a large number of quite small dams to make use of the run-offfrom eroded , impoverished mountain areas。
③The creation of some , 3000 small artificial lakes to provide water for local irrigation has not only very greatly increased production of a wide rang of crops, in some cases by as much as 400 percent, but also ,in bringing water to over 100000 hectares of land , opened the way to a more certain and productive future and higher standard of living for the population in these dry mountain regions。
①一般来说，灌溉被认为是一项耗资巨大的发展措施的最终结果，通常它是以多种工程方案为基础的。
为了更完善地利用整个河流流域的水资源，例如尼罗河流域，就是为了把水带到广大的干旱地区，例如哥罗那亚亚无树大草原和功效中西亚地区②但是并不意味总是非常大规模的建筑工程，如同一篇意大利报纸《论建筑大量小水坝以利用受水侵蚀的贫瘠山区的径流》所表明的那样。
③3000个小型人工湖为当地灌溉提供水源，这些不仅大幅度的增加了粮食产量（有些情况下可达到400%）,而且把水引到10万公顷的土地上，为干旱山区将来获得更高的产量和提高人们的生活水平开创了道路。
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Where irrigation and drainage have been successful……even more spectacular than expected
灌溉和排水计划已经得到成功的地方-——也就是他们已经被条件证明是正确的而且被合理
的计划，已经有效的实施了的地方——效果往往是显著的，甚至比预期的更为惊人。
It is therefore not surprising that……of the development of world agriculture over the last century
因此，这是不足为奇的，为农业目的加强对水的控制（灌溉和排水）乃是上世纪世界农业发展的最显著特征之一。
The areas at present irrigated or drained…..a few million hectares. This development….in most countries.
目前，灌溉或排水的地区总数约为16亿公顷，在20 世纪开始的时，总共只有几百万公顷，在大多数国家中灌溉和排水面积的不断扩大正在加速的持续发展中。
For instance, irrigation areas developed during……during the next 10 or 15 years 例如，在过去的纪念期间，中亚苏维埃共和国所发展的灌溉总面积达50万公顷，而且利用计划表明在未来的10-15年中，其面积可以上升至200万公顷
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None the less, all too often ,…… and the prolonged efforts involved.
尽管有巨额的投资和长期的努力包含其中，然而结果仍是平平常常的，大大低于所预期的，The following are example of the type…….an irrigation or drainage scheme
下述是可能遇到的典型问题，以及灌溉和排水计划可能出错的一类事情。
Lesson 7 soil organic matter
①From very early times husbandmen , and later, scientists have associated this organic matter with soil fertility, and its conservation by addition of organic waste has been widely practiced。
②In more primitive culture, the exhausted soil has been left uncropped to the natural processes that may reestablish its organic content 。
③To this dark material , as to all dark products of organic decay , was applied the name humus, meaning the soil proper as distinct from mere earth。
④The English word “mold”(=muld scand ) had the same significance of refined matter, the essence of soil。
⑤In recent times both words have been degraded to mean organic residues in general , whether decomposed or not, or simply to mean organic matter mixed weth soil。
⑥It is proposed here to use the term humus in the restricted sense of the dark colored finely comminuted organic material which has undergone this change in the soil an , in the crude form, includes other materials not readily separated from it 。
⑦The term humus has of course no strictly chemical definition , but the phenomenon itself and the process by which it is formed , humification , are realities which justify the use of the terms, so long as their sense is not given any exact chemical or physical connotation 。
⑧It will be readily realized that the chemistry of the complex organic mixture present in soil could be effedctively investigated only at a relatively recent stage in the progress of organic chemistry, especially when it is recognized that a large portion of the mixture consists of polymerized substances similar to those carbohydrates , lignins, and proteins that have been the object of intensive research for well over o century and are still only partl understood 。
①很早以前的农民和以后的科学家们都曾经把这种有机体和土壤肥力联系起来，并广泛施加有机废物，以图保持这种有机质。
②在较原始耕作中，采用弃荒的方法，使肥力衰竭的土壤，
感受自然过程，以恢复其有机质含量。
③腐殖质这个名词，就是用来称呼这种暗色物质，也是指由有机物腐烂而成的全部暗色产物，它的含义是表示土壤本体以有别于单纯的土。
④英文单词“mold”,也含有作为土壤本体纯洁物质的同样意义。
⑤这两个词近来被降低为指一般的有机残留物（无论分解与否）或简单的指那些混合在土壤中的有机质。
⑥这里我们建议把腐殖质这个名词的含义限制在土壤中经历变化，而变为暗色，细碎的有机物质，并且包括那些不易同这些细碎有机物质分开的粗的有机物质。
⑦这样看来，腐殖质这个名词，并无严格的化学定义，然而它的形成过程即腐殖化作用及它表现出的现象是真实存在的，这就说明，只要我们不再化学或物理学上给与确切的含义，腐殖质这个名词的应用仍是合理的。
⑧我们很容易体会到存在于土壤中，复杂的有机混合物的化学形成，只有在有机化学进程中的最近时期，才能对它作出有效的研究，特别是我们现在已认识到其中有很大一部分混合物是由聚合物组成的，这些聚合物与碳水化合物，木质素，蛋白质相似，而他们虽已经历了一个世纪以上的深入研究，但仍然只有一部分情况被我们所了解。
As a result of this …….from mere mineral deposits由于有机质分析结果，土壤中发展出现一种棕色到黑色物质，这种物质给予土壤以颜色上的特征并使它有别于单纯的矿物质或体积，从而形成一种非常普遍的土壤特征。
The amount of any one of the………it undergoes decomposition 这种混合物任何一种成分的数量取决于这种成分在活的生物体内的丰富程度和它们的分解速度的大小
Since the major constituents of all green plants are ……should tend to conform to a type因为从整个来看所有绿色植物的主要成分从整体上是相似的，而且，这种成分的分解速度主要受气候和土壤影响，因此我们一般都可以从土壤中发现一般腐烂物的相似成分，而且腐殖质的一般成分应归属为一类。
The central study of soil……..result from these changes土壤有机质的中心研究是探索土壤中植物残体的主要组成和转变作用，以及由于这种变化结果所形成的有机物质
Lesson 8 soil and agriculture
★三段：①A comparison of virgin with cultivated soils is instructive。
Under virgin conditions, soils and vegetation form a system that is in a state of dynamic equilibrium。
②The mineral plant nutrients abstracted from the soil in each season’s growth are returned in leaf fall or by the decay of herbaceous and annual plants 。
③It is true that in forests there is an annual storage of plant food due to tree growth , but in the absence of human interference this material is ultimately returned to the soil as trees die and decay。
④The only losses are in the form of drainage。
Against this may be offset the gains from the weathering of minerals in the soil 。
⑤Under such conditions it is not surprising that luxuriant vegetative growth is possible with a comparatively small supply of available plant food ,of which a considerable proportion is in circulation between vegetation and soil 。
①将未开发的土壤与已开发的土壤对比是有益得。
在未开垦条件下，土壤和植被处于一种动态平衡状态体系。
②在每一生长季节，从土壤中吸取的矿质植物养料，由落叶或草本植物及一年生植物的腐烂而归还给土壤。
③诚然，在森林中，由于树木的生长植物养料每年都有储存，但若不受人类干扰会随树木死亡和腐烂最终归还给土壤。
④唯一损失以排水形式出现。
对于这一点来说，可以从土壤中矿物风化所得到的养料取得补偿。
⑤在这种情况下，这是不足为奇的，即以比较小的有效植物养份的供应是可能使植物茂盛生长的，因为在养料中有相当大一部分是在植物和土壤之间循环的。
★四段：①This equilibrium is completely destroyed when the virgin soil is brought。
